📖 What You'll Learn in This Tutorial:

✓ Understanding Raspberry Pi Pico W pinout
✓ Pico W vs ESP8266/ESP32 differences
✓ Wiring relays to Pico W (safe GPIO selection)
✓ Connecting DHT22, DS18B20, and NTC sensors
✓ Pico W power requirements and BOOTSEL mode

Raspberry Pi Pico W Overview

The Raspberry Pi Pico W is the official microcontroller board from the Raspberry Pi Foundation, featuring their in-house RP2040 chip. Released in 2022, it added WiFi capabilities (hence the "W") to the popular Pico platform, making it an excellent choice for IoT projects.

📊 Pico W vs ESP32 vs ESP8266:

Feature	Pico W	ESP32	ESP8266
Processor	Dual-core 133 MHz	Dual-core 240 MHz	Single-core 80/160 MHz
RAM	264 KB	520 KB	80 KB
Flash	2 MB	4-16 MB	4 MB
ADC Resolution	12-bit (4 channels)	12-bit (18 channels)	10-bit (1 channel)
Operating Voltage	3.3V	3.3V	3.3V
Programming	Arduino / MicroPython	Arduino	Arduino
Price	$6-8	$8-12	$3-5

Pico W Pinout Diagram

                    Raspberry Pi Pico W Pinout
            ┌─────────────────────────────────────────────────────────────┐
            │                                                             │
            │  GP0   ────┐  ┌────  VBUS         ┌───┐                     │
            │  GP1   ────┤  ├────  VSYS         │USB│                     │
            │  GND   ────┤  ├────  GND          └───┘                     │
            │  GP2   ────┤  ├────  EN           ┌─────┐                   │
            │  GP3   ────┤  ├────  GP26/A0      │     │                   │
            │  GP4   ────┤  ├────  GP27/A1      │LED  │                   │
            │  GP5   ────┤  ├────  GP28/A2      │     │                   │
            │  GND   ────┤  ├────  ADC_GND      └─────┘                   │
            │  GP6   ────┤  ├────  GP22         ┌─────────────────────┐   │
            │  GP7   ────┤  ├────  GP21         │   WiFi Antenna      │   │
            │  GP8   ────┤  ├────  GP20         └─────────────────────┘   │
            │  GP9   ────┤  ├────  GP19                                   │
            │  GND   ────┤  ├────  GP18                                   │
            │  GP10  ────┤  ├────  GP17                                   │
            │  GP11  ────┤  ├────  GP16                                   │
            │  GP12  ────┤  ├────  GP15                                   │
            │  GP13  ────┤  ├────  GP14                                   │
            │  GND   ────┘  └────  GP14                                   │
            └─────────────────────────────────────────────────────────────┘

Pico W Pin Functions

Pin	Function	OceanRemote Use	Notes
GP0-GP15	Digital I/O	Available for expansion	3.3V logic
GP16	Digital I/O	Relay 1	✅ Safe for relays
GP17	Digital I/O	Relay 2	✅ Safe for relays
GP18	Digital I/O	Relay 3	✅ Safe for relays
GP19	Digital I/O	Relay 4	✅ Safe for relays
GP20	Digital I/O	Relay 5	✅ Safe for relays
GP21	Digital I/O	Not used	Available for expansion
GP22	Digital I/O	Not used	Available for expansion
GP26 (A0)	Analog Input (ADC0)	NTC Thermistor	12-bit ADC, 0-3.3V
GP27 (A1)	Analog Input (ADC1)	Not used	Available for expansion
GP28 (A2)	Analog Input (ADC2)	Not used	Available for expansion

🔌 Pico W Power Pins:

VBUS - 5V from USB (when connected to computer)
VSYS - 1.8-5.5V input (main power supply)
3V3 - 3.3V output (max 300mA)
GND - Ground (multiple pins available)
ADC_GND - Dedicated ground for analog inputs

⚠️ Important Pico W Pin Notes:

GP0-1 - Used for Serial communication (avoid if using Serial Monitor)
GP2-15 - All safe for digital I/O, no boot constraints like ESP8266
GP16-22 - All safe for digital I/O
GP23-25 - Used for WiFi control (do NOT use)
GP26-28 - Analog input only (cannot output signals)
GP29 - Used for VSYS measurement (do NOT use)

OceanRemote Default Pin Assignments for Pico W

OceanRemote firmware uses these GPIO pins for relays and sensors (all safe choices):

Component	GPIO	Physical Pin	Notes
Relay 1	GP16	Pin 21	✅ Safe
Relay 2	GP17	Pin 22	✅ Safe
Relay 3	GP18	Pin 24	✅ Safe
Relay 4	GP19	Pin 25	✅ Safe
Relay 5	GP20	Pin 26	✅ Safe
Sensor (DHT/DS18B20)	GP15	Pin 20	✅ Safe
NTC Thermistor	GP26 (ADC0)	Pin 31	12-bit analog input
Built-in LED	GP25	N/A	Controlled by WiFi stack

💡 Pico W Advantage:

The Pico W has no boot pin constraints like ESP8266. All GPIO pins (except GP0-1 for Serial and GP23-25 for WiFi) can be safely used for relays without worrying about boot issues.

Wiring Relays to Pico W

Here's how to connect 5 relay channels to your Pico W:

Relay	Pico W GPIO	Physical Pin #	Relay Module Connection
Relay 1	GP16	Pin 21	IN1 → GP16, VCC → 5V, GND → GND
Relay 2	GP17	Pin 22	IN2 → GP17, VCC → 5V, GND → GND
Relay 3	GP18	Pin 24	IN3 → GP18, VCC → 5V, GND → GND
Relay 4	GP19	Pin 25	IN4 → GP19, VCC → 5V, GND → GND
Relay 5	GP20	Pin 26	IN5 → GP20, VCC → 5V, GND → GND

⚠️ Important:

Relay modules typically need 5V power. Connect relay VCC to VBUS (5V from USB) or an external 5V supply. Do NOT connect to 3.3V - relays won't work reliably.

Wiring Sensors to Pico W

DHT22 Temperature & Humidity Sensor

DHT22 Pin	Connect to Pico W
VCC	3.3V or VBUS (5V)
DATA	GP15 (Pin 20)
GND	GND

DHT22 Wiring (Pico W):
┌─────────┐                    ┌──────────┐
│ Pico W  │                    │  DHT22   │
├─────────┤                    ├──────────┤
│   3.3V  ├────────────────────┤ VCC (1)  │
│   GP15  ├────────────────────┤ DATA (2) │
│   GND   ├────────────────────┤ GND (4)  │
└─────────┘                    └──────────┘

DS18B20 Digital Temperature Sensor

DS18B20 Pin	Connect to Pico W
VDD	3.3V
DATA	GP15 (Pin 20) + 4.7kΩ pull-up to 3.3V
GND	GND

⚠️ DS18B20 Pull-up Resistor Required!

A 4.7kΩ resistor must be connected between DATA (GP15) and 3.3V. Without it, readings will fail.

DS18B20 Wiring with Pull-up (Pico W):
┌─────────┐                    ┌──────────┐
│ Pico W  │                    │ DS18B20  │
├─────────┤                    ├──────────┤
│   3.3V  ├────┬───────────────┤ VDD (3)  │
│         │    │               │          │
│   GP15  ├────┼───────────────┤ DATA (2) │
│         │    │    4.7kΩ      │          │
│   GND   ├────┼────[====]─────┤ GND (1)  │
│         │    │               │          │
└─────────┘    │               └──────────┘
               └────────────────┘

NTC 10kΩ Thermistor (Analog)

NTC Thermistor Voltage Divider (Pico W):
         3.3V
          │
          ▼
        ┌───┐
        │NTC│  ← 10kΩ NTC (resistance changes with temperature)
        └───┘
          │
          ├──────► GP26 (ADC0) Pin 31  ← Voltage measured here (12-bit)
          │
        ┌───┐
        │10k│  ← Fixed 10kΩ resistor (R_series)
        │Ω  │
        └───┘
          │
         GND

📊 Pico W ADC Notes:

The Pico W has 12-bit ADC (0-4095) on GP26, GP27, and GP28. This gives much better precision than ESP8266 (10-bit) and is comparable to ESP32. Use GP26 for the NTC thermistor in OceanRemote firmware.

Complete Wiring Diagram

                    COMPLETE PICO W WIRING
            ┌─────────────────────────────────────────────────────────────┐
            │                                                             │
            │  ┌─────────┐      ┌─────────────────────────────────────┐  │
            │  │ Pico W  │      │       5-Channel Relay Module        │  │
            │  ├─────────┤      ├─────────────────────────────────────┤  │
            │  │   USB   │      │  IN1 │ GP16 (Pin 21)                │  │
            │  │  VBUS   ├──────┤  IN2 │ GP17 (Pin 22)                │  │
            │  │   GND   ├──────┤  IN3 │ GP18 (Pin 24)                │  │
            │  │   3.3V  ├───┐  │  IN4 │ GP19 (Pin 25)                │  │
            │  │   GP16  ├───┤  │  IN5 │ GP20 (Pin 26)                │  │
            │  │   GP17  ├───┤  │  VCC │ VBUS (5V)                    │  │
            │  │   GP18  ├───┤  │  GND │ GND                           │  │
            │  │   GP19  ├───┤  └─────────────────────────────────────┘  │
            │  │   GP20  ├───┘                                           │
            │  │   GP15  ├─────┐    ┌─────────────────────────────┐     │
            │  │   GP26  ├─────┤    │        DHT22 Sensor         │     │
            │  └─────────┘     │    ├─────────────────────────────┤     │
            │                  └────┤ DATA │ GP15                 │     │
            │                       │ VCC  │ 3.3V                 │     │
            │                       │ GND  │ GND                  │     │
            │                       └─────────────────────────────┘     │
            │                                                           │
            │                  ┌─────────────────────────────┐         │
            │                  │     NTC Thermistor          │         │
            │                  │  (Between 3.3V and GP26)    │         │
            │                  │  + 10kΩ to GND              │         │
            │                  └─────────────────────────────┘         │
            └─────────────────────────────────────────────────────────────┘

Pico W Power Supply

USB Power (Recommended)

Connect via USB-C cable to computer or phone charger
Provides 5V on VBUS pin for relays
Pico W draws ~100mA with WiFi active
Phone charger (5V, 1A+) works well with relays

External Power (For Permanent Installation)

Connect 1.8-5.5V to VSYS pin
Or use VBUS for 5V (when powered externally)
Relays must be powered separately if using batteries
Total current: ~100mA (Pico W) + 70mA per active relay

⚠️ Power Warning:

The Pico W's 3.3V pin can only provide up to 300mA. Do NOT power relays from 3.3V! Use VBUS (5V from USB) or an external 5V supply for relay modules.

Uploading Code to Pico W (BOOTSEL Mode)

The Pico W uses a unique upload method:

Disconnect the USB cable from your Pico W
Press and HOLD the BOOTSEL button (white button on the board)
While holding BOOTSEL, connect the USB cable to your computer
Release the BOOTSEL button after 2 seconds
A drive called "RPI-RP2" should appear on your computer
In Arduino IDE, select Tools → Board → Raspberry Pi RP2040 Boards → Raspberry Pi Pico W
Select Tools → Port → (no port needed, UF2 upload)
Click Upload - Arduino will compile and copy the UF2 file to the Pico W
The Pico W will automatically reset and run your code

💡 Pro Tip:

You don't need to select a COM port for Pico W. The upload happens via file copy (UF2) over USB mass storage. After first upload, you may need to press the RUN button to restart.

Troubleshooting Pico W

Device Not Recognized / No "RPI-RP2" Drive

Try a different USB cable (many are charge-only)
Hold BOOTSEL button longer (5 seconds) before connecting USB
Try a different USB port
Press the RUN button after connecting

Upload Fails / Stuck at "Looking for drive"

Manually copy the UF2 file from Arduino temp folder to RPI-RP2 drive
Ensure you selected "Raspberry Pi Pico W" (not regular Pico)
Check that the board is in BOOTSEL mode (white LED flashing)

Serial Monitor Not Working

Close and reopen Serial Monitor after upload
Press the RUN button on the Pico W
Check baud rate (115200)
Ensure you're not using GP0/GP1 for other purposes

Relays Not Responding

Verify relay VCC is connected to VBUS (5V) or external 5V
Check relay logic (Positive vs Negative) in dashboard settings
Test GPIO pin with a simple blink sketch before connecting relay
Ensure you're not using analog-only pins (GP26-28) for relays

🔧 Pico W vs Pico:

The regular Pico (without W) does NOT have WiFi. OceanRemote only works with the Pico W. The boards look identical - check for "W" on the metal shield or the WiFi antenna component.

Pico W Special Features

Programmable I/O (PIO) - Can create custom interfaces (NeoPixels, SD cards, etc.)
12-bit ADC - Better analog reading than ESP8266, comparable to ESP32
Dual-core - Can run WiFi on one core, application on the other
USB Mass Storage - Upload code by copying UF2 files (no drivers needed)
Low Power - Can run on two AA batteries for extended periods

💡 When to Choose Pico W:

Choose Pico W for: Python programming (MicroPython), better ADC accuracy, official Raspberry Pi ecosystem
Choose ESP32 for: Bluetooth, more RAM, larger flash, more GPIO pins
Choose ESP8266 for: Lower cost, smaller size, simpler projects

Next Steps

Now that you understand Pico W wiring, continue with:

Tutorial 14: Raspberry Pi 4 / Zero 2W Setup Guide
Tutorial 15: Flashing Firmware to Your Device
Tutorial 16-20: Working with sensors (DHT22, DS18B20, NTC)
Return to Tutorial 02: Generate and flash your firmware!

🎯 You're Ready!

Your Raspberry Pi Pico W is now properly wired. You can now generate firmware from the OceanRemote dashboard and flash your device!

Tutorial 13: Raspberry Pi Pico W - Pinout and Wiring